[Variability of the sleep-wake cycle stages in the laboratory cat]

In order to study the variability of the phases of the sleep-wakefulness cycle (SWC) in the laboratory cat, eight animals were implanted with the standard array of electrodes for EEG, EOG and EMG recordings. Six twenty-four-hour recordings were obtained from each cat at weekly intervals. Three recordings were carried out in the cat colony while the remaining three were obtained with the cat alone in the sound proof chamber. Furthermore, in four cats, other three longitudinal twenty-four-hour recordings were obtained in the sound-proof chamber. In all situations the animals were under a 12:12 light/dark regime and were fed once a day. Sleep recordings were scored according to the polygraphic criteria for wakefulness (W), drowsiness (D), slow sleep (SS) and paradoxical sleep (PS). In each situation a two way analysis of variance (animals and days) was made. Results showed that W, D and SS were the states of the SWC exhibiting the largest variability among animals, while PS was the most stable phase. Variations of the four states among the different days of weekly intervals were not significant. However, a significant increase in PS was observed on the first day in the cases with longitudinal recordings.